The present invention relates generally to a system for setting up and dynamically configuring an optimal routing path for an end-to-end data link connection. In particular, the present invention permits a digital subscriber loop (DSL) user, based on total bandwidth requirements, cost requirements, and/or transfer delay requirements, to optimally configure an end-to-end data path using one or more data routes, including through a regular digital public switching telephone network (PSTN), various kinds of networks (WAN) such as Frame Relay and ATM, or virtual permanent circuit links via digital cross-connects (DCS).
To provide high bit rate transmission over existing telephone subscriber loops, various modem technologies have been proposed. One of the promising solutions is the Asymmetric Digital Subscriber Loop (ADSL) technology that can provide up to 6.144 Mb/s transmission from the central office to a subscriber (downstream) and up to 640 kb/s transmission from the subscriber to the central office (upstream).
As the DSL technology rapidly advances, there is a strong need for the carrier (i.e. phone companies) to provide cost-effective, end-to-end, and high-speed interconnection. However, as explained below, there are many complex issues arising at both the upstream and downstream sites that make it difficult to develop cost-effective and easy-to-install and use solutions.
First, because of the earlier PCM (pulse code modulation) design where analog voice is digitized at a rate of 64 kb/s, the digital telephone switches installed in the Public Switched Telephone Network (PSTN) currently provide only 64 kb/s end-to-end connections. For example, ISDN is a DSL technology that can provide end-to-end circuit switching at a rate of multiple 64 kb/s. Each 64 kb/s link in ISDN is called a B channel and users who want a circuit connection at a rate higher than 64 kb/s needs to use multiple 64 kb/s links at the same time. In this case, all source signals are digital (voice will be sampled to 64 kb/s at the user site) and transmitted over individual B channels. They can be switched by either a digital PSTN 115 or packet switching backbone network 120 as shown in FIG. 1A. In this case, ISDN has the following limitations: (1) The transmission rate over the ISDN line (i.e., from IDSN Network Terminal 110A to 110B) is fixed and cannot be expanded (e.g. basic rate ISDN is 128 kb/s and primary rate ISDN is 1536 kb/s). For high performance services such as video conferencing or graphic file transfers, this data rate is not useful and/or it takes too long in time to transfer. (2) Voice traffic is carried via 64 kb/s PCM or one B-channel. Compared to a typical basic rate access of 2 B-channels, voice connection consumes a large portion of the total bit rate. (3) The protocol for connection over packetswitching backbone network 120 is standardized and requires the other end to follow the same protocol. For ADSL access where transmission rates are in the order of Mb/s, use of a large number of B channels (i.e., multiple ISDN connections) is practically undesirable due to the cost of multiple fixed switched connections. Furthermore, even though the ADSL transmission rate is high, it may not require a constant transmission rate (as is provided by a typical ISDN direct switched connection) all the time for many practical applications such as Internet access.
To overcome the above problems, packet switching (in contrast to circuit switching) based solutions for DSL such as ATM and Frame Relay have been proposed. The term xe2x80x9cDSLxe2x80x9d generally refers to a superset of various digital subscriber loop technologies, including ADSL, HDSL, etc. In particular, WANs (as used herein, xe2x80x9cWANxe2x80x9d refers to any packet-switching based network such as Frame Relay, ATM, or SMDS (Switched Megabit Data Service)) can provide packet-switched based connections at variable rates and have been proposed to support xDSL. An example of a WAN arrangement 180 is shown in FIG. 1B. In this arrangement, connections at a rate other than multiple 64 kb/s between two CPEs 130 and 132 can be established through WAN backbone data network 160 at a lower cost due to bandwidth sharing. Because they are very suitable for data transfer, these types of high-speed backbones have been widely used in LAN interconnections as well. However, they do not guarantee fixed transfer delay. Therefore, they are not suitable for time-sensitive services such as video conferencing. In addition, they require non-trivial network access setups. As a result, they are difficult for ordinary users to install and maintain. To terminate an DSL line 125 and connect it to a WAN 160, a piece of equipment called DSLAM (DSL Access and Multiplexer) 140 is used. As shown in FIG. 1B, a DSLAM splits a subscriber loop 125 to a PSTN 150 for analog voice signals and the WAN 160 for data transmission. As shown, however, the above DSLAM based architecture has the following known limitations. (1) Data transmission always goes through the same backbone data network 160. It is desirable to be able to use the PSTN 150 for switching time-sensitive services. (2) As a result, this type of arrangement does not support end-to-end circuit switching other than Plain Old Telephone Services (POTs), and data communications using voice-band modems.
This prohibits the use of the current suggested DSL xe2x80x9cmodem modelxe2x80x9d in which end-users at CPE 130 can xe2x80x9cdial-upxe2x80x9d any remote site 131, 132 with a compatible modem user model.
Instead, users need to set up all the necessary network addresses for both the host and intermediate nodes. This can be troublesome for most end users and especially a problem when the network needs to be upgraded (i.e. the network is no longer transparent to users). (3) It does not have the ability to split the data signals carried by the DSL 125 into two paths: one through the PSTN 150 and one through the WAN 160. The access to the WAN 160 needs to support the maximum xDSL rate. If not, the high-speed transmission over the DSL becomes wasted. On the other hand, the access cost to the WAN for this type of data rate can be expensive. This poses a challenging problem for the carriers to price xDSL access.
Furthermore, the cost of DSL codecs and access equipment are currently much higher than that of voice-band modems. Therefore, even though the speed is much higher than the current 33.6kb/s or 56kb/s, most end-users will not afford to upgrade this new technology. A lower cost alternative is thus desirable that users can spend less initially for a lower speed and upgrade it at a later time as demands increase.
In addition to the equipment cost, xDSL users will have to spend much more for the access to a high-speed backbone network. In contrast to the current case where modem users do not need to pay any additional cost, this poses another barrier for adoption of DSL technology. Users who subscribe to Frame Relay or T1 access typically need to spend $1,000 or even more every month, a figure which is beyond the means of the majority of potential users of such technology.
A critical need, therefore, exists for a solution that minimizes accesses charges while at the same time allowing carriers to enjoy a reasonable commercial return on their investments in higher end equipment to provide ADSL services. To address this need, a forward compatible and expandable DSL modem or so-called xe2x80x9cSAMxe2x80x9d (scaleable ADSL modem) has been proposed as a low cost solution at the end-user side in pending U.S. application Ser. No. 08/884,995 filed Jun. 30, 1997 entitled xe2x80x9cRate Adaptable Modem With Forward Compatible and Expandable Functionality and Method of Operation,xe2x80x9d also assigned to the present assignee. The invention of that SAM disclosure makes it possible for downstream users to avoid the cost associated with an expensive ADSL modem when they do not need full ADSL transmission rate. In an analogous fashion, it would be attractive and advantageous to extend some of the principles of the above SAM disclosures to the upstream sites. In other words, the central office should be able to effectuate an end-to-end architecture that: (i) permits users to only pay carriers a fee necessary to procure a particular desired target data rate (which may be only a fractional portion of a full ADSL data link); (ii) allows users to establish a particular kind of data link (real-time or delayed); (iii) allows users to accept the lowest cost per unit of bandwidth; or (iv) facilitates a data route which is more suited to particular user""s connection model.
Accordingly, an object of the present invention is to provide an end-to-end architecture and system that permits users to flexibly, transparently, and dynamically configure high-speed connections based on criteria such as their particular data rate needs, associated costs of using various data paths, bandwidth availability, access costs, and suitability to the user""s connection model.
Another object of the present invention therefore is to provide an access and multiplexing circuit for use in a central office that permits a user to configure and control an end-to-end connection, including a target data rate, via either the current digital PSTN, a packet-based WAN interconnection, or a digital cross-connect.
A further object of the present invention is therefore to provide a flexible and efficient access and setup process for permitting DSL users to configure and control an end-to-end connection, including a target data rate and connection path via either the digital PSTN, a packet-based WAN interconnection, or a digital cross-connect.
Yet a further object of the present invention is to provide an end-to-end connection that is still nevertheless backwards compatible with existing subscriber loop access protocols and is also forwards compatible with proposed partial DSL bandwidth CPE/ISPs at downstream sites.
Yet another objective is to provide a new DSLAM architecture that allows users to incrementally pay for the access fee according to their speed and service requirements.
The objects of the present invention are effectuated by providing a system that establishes an end-to-end data path connection between a data link requesting site and a destination site based on a data route request provided by a user at the origination site. At the central office site, an interface circuit receives voice, data, and the data route request signals from a digital subscriber loop (DSL) coupled to the user""s device at the origination site. A data routing control circuit then evaluates and sets up a data route between the origination site and the destination site using the most optimal data path matching the user""s request. This data path can include any one or more of the following: (i) a circuit switched PSTN; and/or (i) a wide area network (WAN); and/or (iii) a digital cross-connect. Other data paths compatible with a PSTN and WAN are also possible. After the link is established, an access router is then used for routing the user""s data through the selected data path.
Each of the various data paths has its transmission characteristics, including among other things, a maximum data rate, transfer delay, cost per unit bandwidth, connection model, etc. In the data route request, the user can specify any requirements for these and similar parameters, and the routing control circuit determines which of the available paths most conforms to such request, thereby effectuating a data path most suited for the user""s needs. For example, if a very high speed link is required (in excess of 128 Kbs), a WAN may be selected, so long as the other user defined constraints are met by such data path. This type of data path optionally transfers data using any or all of the following: frame relay, and asynchronous transfer mode (ATM). In determining the data transfer rate of any path, the system also takes into consideration the capabilities of any digital subscriber loops coupled to the various communicating sites, as well as the data processing capabilities available at these sites. For time delay sensitive applications, such as video teleconferencing, a switched network, such as the PSTN may be used instead. This can be achieved by setting up one or more dedicated 64 Kb/s links. Similarly, if low cost is the most important specified criterion in the request, the system can also dynamically determine and select the data path having the lowest cost per unit of bandwidth at the time of the request. In a preferred embodiment of this system, the interface circuit also separates the data into voice signals and DSL signals. A pulse code modulation circuit then converts the voice signals into digital voice signals for routing through the switched network. The access router is coupled to all the available data paths, including (i) a circuit switched PSTN; (i) a wide area network interface circuit; and (ii) a digital cross-connect interface circuit An access and setup process is also described for accessing and configuring a variety of optimal end-to-end data path modes, including end-to-end switching through a PSTN, end-to-end switching through a WAN, and through an xe2x80x9calways-onxe2x80x9d type connection. First, a user initiates a connection and transmits an access request to a local central office. The access request can include information concerning a requested data route, target data rate, user connection model, desired cost for the transmission, etc. At the central office, determination is made concerning whether the access request is related to voice signal transmission or a data signal transmission. Based on the parameters of the request, a data route is configured to accomplish the data transfer. The access request can specify a particular data path, or alternatively, can specify that a DSLAM circuit in the central office should select a particular access mode (i.e., the most optimal data path matching the access request requirements) for transmitting data.
In an embodiment where an end-to-end connection is requested through the PSTN, a data path at a data rate of some multiple of 64 kb/s can be set up for applications, which, for example, require realtime performance. After requesting a data path at a particular target rate requested by the user, an evaluation is made of the line qualities between the CO and the communicating sites to ascertain the target rate. The PSTN then allocates and sets up multiple available 64 kb/s connections to try and satisfy the target rate transmission. Thereafter communications can proceed between the two sites at such rate.
In another embodiment where an end-to-end connection is implemented through a WAN, a data path at a certain target data rate can be set up for applications which require a higher data rate, or as is often the case, a lower cost per unit of bandwidth. As above, after requesting a data path at a particular target rate, an evaluation is made of the line qualities between the CO and the communicating sites to ascertain the target transmission rate. The WAN then allocates and sets up sufficient bandwidths to try and satisfy the maximum target transmission data rate. Thereafter communications can proceed between the two sites at such rate.
In applications where a permanent, xe2x80x9calways onxe2x80x9d DSL connection exists to the central office, a slightly different process can be used. First, to start the connection (turn it on initially) a negotiations procedure is effectuated which determines the highest achievable rate X available through the DSL connection. A WAN having a particular available rate Y is used for effectuating the end-to-end packet-switching connection (i.e., by Frame Relay or ATM) at a rate which is the lesser of X and Y. In the case where Y is smaller than X, a reduced rate Y is proposed to the origination site, which can accept such proposal, or reject the request. A similar negotiation procedure is effectuated at the destination site to determine the maximum rate achievable by that site""s DSL. If both sites confirm the request, an end-to-end connection is established for data transmission.
The architecture of the present system combines current DSLAM functions (ATM and/or Frame Relay accesses) with user-configurable end-to-end circuit switching capability. That is, users can decide the rate and ask for connection via either the current digital PSTN packet-based WAN interconnection, or virtual permanent DCS connections. The choice they make can be based on their particular service requirements and the cost they are willing to pay for such service on a call by call basis. The present invention can be loaded directly on top of preexisting switching network infrastructures, and furthermore, permits carriers to more easily allocate the cost of routing data in a manner proportionate to the service requested by a user. For example, an appropriate cost allocation can now be made for delay-sensitive services that require direct switched connections, as opposed to non-delay sensitive services, such as Internet access, which only require packet switching (or the like) connections. Therefore, it provides a smooth migration for all current modem, ISDN, and LAN users. Furthermore, when used in combination with a SAM type transceiver at the end-user side, it provides a very low-cost, end-to-end solution for users who need only connections at a data rate around several hundred kb/s but want to reserve the option of upgrading to a higher performance standard at a later time.